Garden or hedge shears



Feb. 20, 1940. w. G, MCDONALD 2,191,236

GARDEN 0R HEDGE- SHEARS Filed June 18, 19s? misnomer, as my blades aredefinitely cutters. greaterdegree of efficiency than the conventional 35They are not suitable to operate on thin paper, type shown in Fig. 3.The advantages being, light fabric, or sheet metal, but on substancesthat for any degree of blade opening there is with some body in themsuch as card-board, available for use, a greater amount of cutting 40leather, rubber, klinkerite and other packings, edges and the anglebetween the two cutting 40 they are very efficient. edges is greatlydecreased, thus reducing the r I am aware of many prior arts in relationto forward thrust on the material as the blades close improvements inhand shears, most of which seron it. a-a are radius lines on theextremity of rate one blade only. The types of notches and the arc ofblade opening. The cutting edge of serrations are many, also others havetreated both each blade is approximately parallel to a-a. 45 blades. Myinvention is distinct and differs from The ordinary type of bladeshavetheir cutting all the prior arts Ihave been able to learn of. edgesillustrated in the dotted lines b. The

Passed Feb. 20, 1940 2,191,235

" UNITED STATES PATENT OFFICE t I oaanmv- 02 :3; slinsas I Q I itWilliam emmmcnomm, EastSt. Kilda,

.Yitoria, Australia, Application June 18, 1937, Serial No. 150,600 i InGreat Britain February 11, 1936 i 2 Claims. (01. co -s55) My inventionrelates to improvements in cut- Figure 2 is a face view of a pair ofblades deting tools, having two blades working radially signed tofurther increase their emciency in the on a pivot-bolt or screw. It isthe general cusprevention of forward slip of material requiring tom forthe blades of such shears to have plain cutting.

or straight uninterrupted working edges, but a Figure 3 is a crosssection taken on the line 5 disability attendant thereon is that whenat- VV of Figures 1 and 2. tempting to cut through various objects, suchas Figure 4 is a part cross section, on a greatly for examplecomparatively tough or stout stems, j enlargedscale, taken on line IVIVof Figures twigs or other growth, the objects tend to slip or 1 and 2. i

be forced forward, as the blades close on it or Referring to the drawingit will be seen that 10 them, and escape from the outer ends :or tipsthe bevels forming the cutting edges on both thereof without beingsevered. This is due in blades 6 are stepped, thus forming a series ofpart to the fact that the cutting edges are genkeen cutting wedges inpairs, each pair being erally ground to a shearing anglethis being theprecisely opposite one another. This stepped l5 lesser of two evils.When the plain edged blades bevel has a continuous cuttingedge, the rearporare ground to a keen cutting angle the amount. tion of each wedgeforms the tooth I. The abutof slip betweenthe material and the bladesrapment edge 8 may be straight but is preferably idly dulls theircutting edges. With blades ground curved as shown between I and 9 itshould be as herein described the slipping propensity is reshort orshallow, nothing is gained by increasing duced to a minimum. The seriesof keen edged. the depth of 8; rather it would add to the diifi- 20cutting wedges are like a number of wood chisels culties of producingthe facet I0 on the inner secured edge to edge, the rear portion of eachone side of the cutting edges dead accurately. projecting a little aheadof the front portion of Theoretically the angle of facet II) should be,that next behind it. The physical property of a the plane of blademovement represented by the wedge, to d ve into Work in the directionwhich dotted line Figs. 3 and 4. Actually several de- 25 bisects its ownangle, causes these blades to be tails have a bearing on this angle I0.They are, forced together by the pressure of the work on the set of theblades both longitudinal and transthe outer level of each pair ofcutting wedges. verse, the flexibility of the blades and the pres- Thenatural wear thus produced keeps the edges sure of the work being cut onthe outer bevels 5 perfectly keen, in fact natural wear produces a ofthe wedges. Fig. 4 shows this facet Ill ground 30 keener and truer edgethan is possible to obtain to the line 9-9 which is a little in excessof the by grinding on the stone. true angle, natural wear will very soonmake All substances to be severed in the garden are this facet or seriesof facets perfect along the wood; wood should be cut, not sheared. Theentire length of the blades.

word shears, in relation to my invention, is a Figure 2 illustrates apair of blades having a In order that this invention may be betteramount of cutting edges, their angles, and the understood, referencewill now be made to the difference between the amount of blade availableaccompanying sheet of drawings, which are to for cutting, in each typeare illustrated at c and 50 be taken as part of this specification andread d, Fig. 2. I herewith: Having now particularly described and ascer-Figure 1 is a face view of a pair of blades of tained the nature of mysaid invention and in the conventional type, with their cutting edgeswhat manner the same is to be performed, I deground in accordance withthe invention. clare that what I claim is: 55

1. Improvements in and relating to garden or hedge shears and the like,wherein each blade is provided along its cutting edge with a series ofstraight edged cutting wedges forming shallow recesses in said edge, theblade members being turned at an angle to the plane of blade movementand each cutting portion of the blade having a beveled outer portionsloping towards the inner face of thelblade member at a small acuteangle, the inner wall of the blade having its cutting portion formed bya. short beveled portion extending from a line slightly below the bottomof the shallow recesses in the cutting edge and substantially in theplane of blade movement and sloping at a. sharp acute angle to the planeof blade movement and meeting the first said beveled portion to formasharp cutting edge,

each of the above mentioned wedges being ground to a knife edge andterminating at its forward end in a short curved cutting edge whichconnects it to that wedge next in front of it, so as to providethroughout the length of the series of wedges, a continuous steppedcutting edge; de-

void of anyshearing or noncutting portions.

2. Improvementsin and relating to garden or hedge shears and the like,as claimed in claim 1, wherein both blades are provided with a series ofstraight edged cutting wedges and curved abutmentedges, each of which isprecisely opposite that of its fellow on the opposite blade, so that theabutment edges co-operate in cutting and preventing the work fromslipping, and the wedges provide, with the pressure of the work on theirouter bevels, an equal and even pressure on the inner edge of each bladewhilst entering the work.

WILLIAM GRANT McDONALD.

